Typically, a process of processing substrates for devices such as an LCD, OLED, and SOLAR needs a sealed chamber for performing a predetermined process under a high vacuum atmosphere, such as a thin film depositing process and an etching process. Further, to increase substrate yield through the chamber, it is important to maintain an inside of the chamber without any contaminants.
The chamber includes a process chamber (PM) in which a predetermined substrate treatment process is performed under a high vacuum condition, a load lock chamber (LM) in which a substrate is loaded or unloaded, and a transfer chamber (TM) which is installed between the PM and the LM to transfer the substrate.
Meanwhile, a slit serving as a passage through which the substrate passes is formed between the chambers, and a slit valve is installed at the slit to open/close the slit.
The slit valve serves to open/close the slit substantially forming the passage between the chambers. The slit valve includes a valve plate having the same shape as that of the slit and a larger size than that of an opening of the slit, an actuator operated by air pressure to drive a shaft connected to the valve plate and thus to lift up and down the valve plate, and the like.
Further, an o-ring 3 for sealing the slit 2 is provided at a portion of the valve plate 1 which is in contact with the slit 2. When the slit 2 is closed using the valve plate 1, the valve plate 1 is pressed to a side of the chamber, and the o-ring 3 is compressed, and thus the slit is sealed.
However, as illustrated in FIG. 1, in a conventional vacuum processing apparatus, since the slit 2 as the substrate passage between the chambers is closed by one valve plate 1, when a vent process in which a gas such as nitrogen is injected to maintain one of the adjacent chambers in an atmospheric pressure state is performed, a pressure difference between the two chambers becomes very large. And the valve plate 1 sealing the slit 2 is pushed from the chamber having high pressure (in which the vent process is performed) toward the chamber having low pressure (which is maintained in the vacuum state).
At this time, when the PM is the chamber having the high pressure (in which the vent process is performed), the valve plate 1 is pushed to the TM by the pressure difference, and also counter-pressure is generated. In this case, a fine gap is generated at a contact surface between the o-ring 3 and the slit 2, and has an influence on a vacuum state of another adjacent chamber. Finally, this causes a defect in the process, and thus leads to a defect in products.
Particularly, since the substrates are recently turned out on a mass production basis, a multi-process chamber type vacuum processing apparatus in which the plurality of process chambers adjacent to the transfer chamber disposed at a center portion of the apparatus are provided and thus the plurality of processes are simultaneously carried out in one apparatus is widely used.
In this case, when one of the plurality of process chambers is in trouble, or the vent process should be performed at the process chambers due to a periodical check, the transfer chamber used as a common chamber should be maintained in the vacuum state, and thus other process chambers may normally perform the process.
However, in the multi-process chamber, when the vent process is performed at one of the process chambers, interleakage occurs between the process chamber in which the vent process is performed and the transfer chamber due to the counter-pressure caused by the pressure difference therebetween, and the vacuum state of the transfer chamber is released, and the vacuum states of other process chambers are also affected, and thus the defect occurs in the entire process.